Tell me why (motor drag content)

[2WheelsNot4]

Right ok, im cycling down a hill(road) doing approximately 23mph. Lowest cog and turning the,pedals is difficult. As in there is resistance in them, presumably from the motor.
So pedaling isnt really increasing my speed, it only seems to limit the power i can put in.
Naturally I cannot watch the speedometer constantly as im in a line of traffic, which could cause me to drift into dangerous territory. but i certainly didnt feel like i was increasing my speed, only limiting my ability to do so.
It really is the strangest sensation.

 

[flash]

Most motors have little drag, in reality.

What bike, motor, tyres, pressures?

Gordon

 

[Twonks]

You could also be suffering for what I called Motor Blindness. I too felt exactly the same when I was on the road trying to pedal past 15.5mph on my new emtb. It felt like once past the motor assistance, there was a huge amount of treacle holding me back.

To my surprise, this same treacle got stuck under the wheels of my regular non electric bike (when taking it out a few weeks after only riding the new eeb) with even the slightest incline leaving my house - an incline that has never been an issue or thought about at all previously.

Took quite a way into the ride to get used to it again and I surmised that the motorised bike was not actually dragging that much in reality, more so I had got used to just how much assistance it gave.

If you have a non electric bike OP, maybe try ride it back to back with the emtb and see if you find the same.
At 23mph on an mtb down anything less than a sizable hill, I'd expect a reasonable amount of power required to be put into the cranks.

 

[Alexbn921]

Motor stops helping and you need to triple your out to maintain the speed. Motors don't really drag.

 

[mxh]

Motors don't really drag.

I'm riding a bike with a 4 year old Shimano E8000 motor, and it definitely feels like it hits a brick wall when it reaches 25kmh. So first thoughts in reply to that statement are "yes, they do". But in reality, how much of that is (as Twonks mentions) due to it actually being difficult to increase speed on ANY mountain bike (with draggy tyres etc) when you reach that speed.

Has anyone done any tests to see how different motors compare? I assume that should be as easy as just pedaling them with the motor switched off, or more scientifically seeing how much force is required through the pedals compared to a free running analog setup?

I'm looking to upgrade my bike at some point in the near future - I'm finding this 'brick wall' more and more of an issue with the sort of riding I'm doing and if there were a difference in drag between motors, that could have an influence on what bike I go for next.

 

[Alexbn921]

Most if not all motors have basically zero drag. The wall is just the motor turning off and then you need to make up that power.

 

[mxh]

Most if not all motors have basically zero drag. The wall is just the motor turning off and then you need to make up that power.

Shimano claim that the EP8 has a 36% reduction in drag compared to the E8000. By even mentioning this they recognise that motors do indeed have drag, and also that the older motor (the one I've got) has more drag than their current one.

So even if drag is minimal, it's still there - and I'd be interested to know which motors have the least after the 25kmh cut off.

 

[Mteam]

There's minimal drag from most decent motors used by emtbs.

Just put your emtb in a workstand and turn the cranks by hand with the motor switched off, then repeat with your normal MTB in the same gear, you'll find they feel very similar. Or take the chain off the emtb and turn the cranks by hand,you'll feel similar resistance to doing that on a normal mtb

The drag you feel at the cut off speed is because you suddenly have to produce 250w ( or whatever) more than you were producing when the motor was doing it's thing.

 

[rod9301]

Most if not all motors have basically zero drag. The wall is just the motor turning off and then you need to make up that power.

True, I'm wondering if people are actually retarded for thinking there's drag

 

[mxh]

Just put your emtb in a workstand and turn the cranks by hand with the motor switched off, then repeat with your normal MTB in the same gear, you'll find they feel very similar. Or take the chain off the emtb and turn the cranks by hand,you'll feel similar resistance to doing that on a normal mtb

OK, I did. I removed the chain on my e-bike and my analog bike and tried 2 things. Firstly to spin the crank and see how many revolutions it did until it stopped. And secondly I put the cranks horizontally and added weight to the pedal until it moved. I did them both several times, especially the spin test to ensure that I was applying the same amount of force on each spin..

Analog bike - max of 4 revolutions and approx 20 grams
E-bike - max of 2.5 revolutions and approx 60 grams

I'm the first to admit that with a sample size of 1 of each bike it's not particularly scientific, but at least it's an actual test. But it is an old E8000 engine, which I'm sure isn't as good as the current crop of motors. Would be interesting to see how a new motor fares (anyone up for trying?)

The drag you feel at the cut off speed is because you suddenly have to produce 250w ( or whatever) more than you were producing when the motor was doing it's thing.

I'm not doubting this - and the cut off makes it feel much worse than it actually is.

True, I'm wondering if people are actually retarded for thinking there's drag

Like the people at Shimano you mean? Those retards claim that the EP8 has 36% less drag than the E8000. What would they know?

 

[Mteam]

OK, I did. I removed the chain on my e-bike and my analog bike and tried 2 things. Firstly to spin the crank and see how many revolutions it did until it stopped. And secondly I put the cranks horizontally and added weight to the pedal until it moved. I did them both several times, especially the spin test to ensure that I was applying the same amount of force on each spin..

Analog bike - max of 4 revolutions and approx 20 grams
E-bike - max of 2.5 revolutions and approx 60 grams

I'm the first to admit that with a sample size of 1 of each bike it's not particularly scientific, but at least it's an actual test. But it is an old E8000 engine, which I'm sure isn't as good as the current crop of motors. Would be interesting to see how a new motor fares (anyone up for trying?)

sounds right to me - and in the context of how much pressure your legs can exert an extra 40 grams is nothing.

 

[Jurassic]

I've just spent the last few days riding my non eeb gravel bike after riding solely my eeb for the preceding three weeks. I expected the gravel bike (which is nice and light with quick rolling wheels and tyres) to feel lively. In reality for the first couple of hours it felt like riding in treacle compared to the eeb. I've also ridden my eeb to the bottom of the trails with the motor turned off just to see what it's like and it felt fine on the flat (although any type of a climb was hard work due to the weight of the bike) but riding it past the cut off with the power on feels awful. This leads me to believe that there's very little drag from the motor on my bike. It's a Giant Reign with the Yamaha PWX3 fwiw. Interestingly my wife has an older Cube hardtail with a gen 2 Bosch motor and that feels even more draggy above the cut off than my bike so maybe the older bikes do suffer from more motor drag.

 

[Mteam]

I've just spent the last few days riding my non eeb gravel bike after riding solely my eeb for the preceding three weeks. I expected the gravel bike (which is nice and light with quick rolling wheels and tyres) to feel lively. In reality for the first couple of hours it felt like riding in treacle compared to the eeb. I've also ridden my eeb to the bottom of the trails with the motor turned off just to see what it's like and it felt fine on the flat (although any type of a climb was hard work due to the weight of the bike) but riding it past the cut off with the power on feels awful. This leads me to believe that there's very little drag from the motor on my bike. It's a Giant Reign with the Yamaha PWX3 fwiw. Interestingly my wife has an older Cube hardtail with a gen 2 Bosch motor and that feels even more draggy above the cut off than my bike so maybe the older bikes do suffer from more motor drag.

I think the gen 2 bosch was known to have some noticeable drag from the motor over the cut out speed.

 

[Jurassic]

I think the gen 2 bosch was known to have some noticeable drag from the motor over the cut out speed.

Yeah that sounds about right then.

 

[RustyIron]

Analog bike - max of 4 revolutions and approx 20 grams
E-bike - max of 2.5 revolutions and approx 60 grams

This is an an interesting observation. The fun thing about gathering data... and sometimes the controversial part... is deciding which data are relevant. Your observations are relevant in that they debunk the fanatical beliefs of some riders that the motor is to blame for their inability to go fast.

I tip the scales at 89 kilograms buck naked. Usually I ride with clothes, so let's round it up to 90 kilos.

When I'm pedaling hard and standing on the pedals, I'm giving it 90 kilograms downward force, or in my quick estimation, 90,000 grams. By your measurement, the motor clutch burns up 40 grams of force. With these two pieces of data, we now know that the motor requires 0.04% extra force to move the crank. Is there anyone here who can feel an extra 0.04% increase in drag? I can't.

The "drag" felt by some riders is not drag at all. It's just that their motor turns off at that speed, and they're not used to using their own power to make a bike go that fast. Wind resistance is a mo@#$ fu$%@*, brother.

Other differences that make most eMTB's more difficult to pedal is that they are HEAVY. My eMTB weighs 65% more than my aMTB. It also has slower rolling tires. Before anyone starts gnashing their teeth and yelling about how motor manufacturers are stupid, put some real DH tires on your Acoustic Mountainbike, then throw a 20 pound case of ammo in your Camelbak, and now spin that bike up to 25 mph and hold it there. I'll bet it's harder to go fast, isn't it?

 

[RustyIron]

because you have to spin all this around with no power it is like hitting a brick wall.

Really? Your motor doesn't have a clutch, so all the gears and motor spin when you pedal with no power? That sounds awful.

 

[Mikerb]

I have 2 emtbs...........one long travel enduro and one more trail/all mountain. Both are similar weight and equipped with similar tyre specs. The trail/all mountain bike is however far more pedal efficient albeit nowhere near as pedal efficient as a hardtail mtb or hybrid bike. It is however far easier to ride over the motor cut off speed than the more enduro focussed bike.

I know if I am riding a trail where it is possible to maintain a speed close to the cut off ( which the Kiox on my Bosch Gen 4 tells me is at 16.4 mph) I need to be in one gear lower and increase cadence if I want to go faster. At close to cut off speeds I am invariably in a pretty high gear and the bike has good momentum so my power input is minimal compared to the motor input so when the motor shuts off there is potentially a big transition.....but only if there is something to kill the bike's momentum such as an incline, rougher trail conditions or a headwind. If none of those apply I actually find it quite difficult to determine if the motor has cut out or not, especially if I preempt it by going to a lower gear and increasing cadence.
So does the motor have drag? Well there is more to rotate on the crank on an EMTB (albeit the motor is disengaged) than on an analogue bike but characteristics like bike weight, draggy tyres, and low anti dive kinematics ( in favour of rear wheel bump compliance) have significantly more effect.

 

[Alexbn921]

because you have to spin all this around with no power it is like hitting a brick wall.

View attachment 97719
View attachment 97720

You can see the roller bearing for the crank arms. None of that is spinning unless the motor is making it

 

[mxh]

The fun thing about gathering data... and sometimes the controversial part... is deciding which data are relevant.

Very true

When I'm pedaling hard and standing on the pedals, I'm giving it 90 kilograms downward force, or in my quick estimation, 90,000 grams. By your measurement, the motor clutch burns up 40 grams of force. With these two pieces of data, we now know that the motor requires 0.04% extra force to move the crank. Is there anyone here who can feel an extra 0.04% increase in drag? I can't.

I'm not sure this is really relevant. The weight required to get the crank moving is about overcoming inertia - when you're pedaling and the cranks are already moving, you're not trying to overcome this initial inertia.

I think the more interesting test was spinning the cranks. The analog bike was definitely more free running (and don't forget this is with the chain off, so nothing to do with the drivetrain). The analog bike crank span for 60% longer than the e-bike crank. That quite definitively shows that IN THIS COMPARISON there is more drag on the e-bike. But how much extra force would I need to overcome this drag at 25kmh? I've got no idea - it certainly wouldn't be 60 %, but would it be something noticeable? Or would it be so small as to be irrelevant? Any maths geniuses able to do the sums?

 

[Akiwi]

It is amazing how often this topic comes up!
I start all my rides initially with the motor off, and get used to the bike without assist, then turn the motor on when I need it.
It helps to not get spoilt.
I guess it depends on what / where you ride. I do a lot of touring / adventure riding where minimal battery use is important. So, I have got used to riding on the flat or slight inclines without assist, and use Eco where most other people are already on tour or EMTB.
I did notice a reduction in drag when I changed from the Bosch Gen 2 motor with the gearbox, to the newer Gen 4 without.

It seems that 25 kph is a bit of a magical drag barrier. On the flat, without any assist, I can easily get to 25 kph, but going above always seems to require more effort.

 

[RustyIron]

It seems that 25 kph is a bit of a magical drag barrier. On the flat, without any assist, I can easily get to 25 kph, but going above always seems to require more effort.

Math and physics are indeed magical.
The force of air resistance increases by the square of the increase in velocity.
We experience it first hand when as we ride faster.

 

[mxh]

I did notice a reduction in drag when I changed from the Bosch Gen 2 motor with the gearbox, to the newer Gen 4 without.

And do you have an analog bike as well? If so, do you notice any difference in drag between the two (assuming other things like tyres etc are similar)? Or would you say that your current motor has no more drag the analog bike?

 

[Jurassic]

And do you have an analog bike as well? If so, do you notice any difference in drag between the two (assuming other things like tyres etc are similar)? Or would you say that your current motor has no more drag the analog bike?

Yeah, I have an Orbea Rallon, a fat bike and a gravel bike as well as the ebike. I think the ebike feels like it has more drag when I ride with the motor switched on and go above the threshold but if I ride with the motor switched off it just feels like a very heavy bike which leads me to believe that any drag must be minimal. I think the drag that I feel when I go above the cut off is probably just the contrast between feeling the assistance (below the cut off) and losing that extra help when I go over the cut off. All seat of the pants stuff and not based on any kind of science though.

 

[Akiwi]

And do you have an analog bike as well? If so, do you notice any difference in drag between the two (assuming other things like tyres etc are similar)? Or would you say that your current motor has no more drag the analog bike?

I don't have an analog bike with a similar setup, however I am 100% convinced that people just get used to the assist, and when they turn it off, it feels like riding through treacle.
I have a city bike for commuting, and honestly, if I ride the emtb without assist it isn't really that different. Just heavier, and has fat knobby tyres.
Like I say, I ride a lot without using the motor, and you get used to it.